The present invention relates to a composition of matter and a process to make it. In particular, the composition is a microporous or mesoporous material fabricated by a method that uses high solids materials processing.
The prior art includes two standard methods for materials processing for either crystallization or precipitation. The first is the standard autoclave crystallization process using commercially available equipment in a batch operation. This is the preferred approach to crystallizing microporous and mesoporous materials. The reaction mixture is stirred to assure uniform composition of the product. The finished product is typically washed, sent through a filtration system, and then dried for further processing. A second approach is a continuous precipitation process, producing a product that again requires filtration prior to further handling.
The present invention addresses materials synthesis and processing. There is also a need and desire for efficient exploration of high solids synthesis regimes. The typical approach in hydrothermal synthesis is to use autoclaves in a batch operation. Autoclaves are pressure vessels capable of withstanding the autogeneous pressures generated at crystallization temperatures in the 100-250° C. range. Autoclaves are cumbersome and manpower intensive. The present invention uses a continuous feed system that is more semi-continuous to continuous operation, dependent upon the configuration of the equipment, the feed, and reaction conditions required for the crystallization.
The present invention allows the evaluation and manufacture in high solids regimes. Typical batch crystallizations are run at relatively dilute suspensions, up to 15% solids. Current commercial autoclave technology cannot process reaction mixtures substantially in excess of about 15% solids because they are too thick to stir effectively. Inadequate stirring in a large, batch reactor leads to improper heat transfer and inadequate temperature control. Laboratory experiments are typically done on small scale where a uniform solid can be crystallized in a static operation. The process of this invention allows continuous throughput of the reactants. With suitable internal design of the rotor, the continuous process can mimic either static or stirred conditions as the reactants are transferred through the barrel. Adjusting the feed rate controls residence time. Also, adjusting the auger speed for an auger in a barrel configuration or adjusting the barrel rotation speed in a rotary calciner configuration impacts the residence time.
The use of continuous reactor processes is well known, particularly in the polymer area. For example, many processes for polymers that may be carried out continuously in extruders (see e.g., Reactive Extrusion, Principles and Practice, Xanthos, M., ed., Hanser Publishers, 1992). The advantage of such processes for continuously varying the product by varying the reagents is also known. For example, polymer properties may be controlled by adjusting the rate of periodic batches of manganese dioxide (see e.g., Suwanda, D.; Lew, R.; Balke, S. T. J. Appl. Polym. Sci. 1988, 35, 1019. “Reactive Extrusion of Polypropylene I: Controlled Degradation”). It is also known that the product may be controlled by continuously varying the temperature and reaction time by controlling the total feed rate to the extruder (see e.g., Xanthos, M. in Reactive Extrusion, Principles and Practice, Xanthos, M., ed., Hanser Publishers, 1992, page 44). It is also known that reagents may be added not only in the initial feed hopper but at points along the reaction path by injecting reagents into the extruder or by using tandem extruders (see e.g., Todd, D. B. in Reactive Extrusion, Principles and Practice, Xanthos, M., ed., Hanser Publishers, 1992, page 203 ff). This process is called “staging.” It is also known that the process of continuous reaction may be used as a research tool to produce large numbers of different materials by varying the feeds (see e.g., Nelson, J. M.; Davidson, R. S.; Cernohous, J. J.; Annen, M. J.; McNerney, R.; Ferguson, R. W.; Maistrovich, A. R.; Higgins, J. A. US 2003/0035756A1, Feb. 20, 2003. “Continuous Process for the Production of Combinatorial Libraries of Materials”). It is also known that there are some favorable conditions under which hydrothermal synthesis may be carried out in a low solids (high dilution) environment (see e.g., Rollmann, L. D.; Valyocsik, E. W. U.S. Pat. No. 4,374,093, Feb. 15, 1983. “Continuous-Stream Upflow Zeolite Crystallization Apparatus”). It is also known that under some circumstances it may be possible to carry out hydrothermal synthesis under high solids conditions (see e.g., Miller, S. J. U.S. Pat. No. 5,558,851, Sep. 24, 1996. “Preparation of Aluminosilicate Zeolites”).
The present invention discloses high solids, continuous or semi-continuous hydrothermal synthesis of microporous or mesoporous materials. This invention will accelerate the discovery of new materials in the high solids crystallization regime. The process allows for faster throughput and in-situ modification of the synthesis by varying what reagents are introduced when in the crystallization process. In addition, elimination of extraneous liquor allows for decreased inventory of hazardous materials as well as a decrease in subsequent mother liquor obtained after crystallization or processing.